#include<iostream>
#include<math.h>
using namespace std;
double check(double mid){
	double k=-1*mid;
	double a=k*k+2*mid+1;
	return a;
}
int main(){
	double l=-10,r=1,mid; 
	while(fabs(l-r)>0.001){
		mid=(l+r)/2.0;
		cout<<mid;
		double a=check(mid);
		if(a==0){
			break;
		}
		else{
			double m=max(l,r);
			if(l<=r){
				l=mid;
			}
			else{
				r=mid;
			}
		}
	}
	cout<<mid;
}
